'95 - E350, 351. runs smmoth, nice power, but idles @ 1400 rpm? where do I start? stuck throttle? I just bought this so I have no idea how long it's been a problem. It's great on the highway, but a pain in town.

 

I am currently chasing this issue on my 91 bronco with 5.8, and here is my advice to you. First, pull the codes!! Dont go replacing parts after pulling the code either because it has only given you an idea where to start. Second, check for vaccuum leaks. Take the vaccuum harness out and Mark! where the line came from and how it goes back on to the engine. Open the loom up and see if any of the lines are broken, cracked, or otherwise in poor shape. Replace the line with new hose if need be. Third, get out the multi meter and test the continuity of every sensor wire to the computer harness. Fourth, test the resistances and voltages from each sensor, fordfuelinjection will give you the appropriate test range of each sensor. Fifth, check to make sure that the throttle linkage is not binding so that it does not allow the throttle valves to close fully against the throttle stop. Sixth, check the IAC motor, the motor that controls idle. You can clean the throttle body and IAC if there is a carbon build up around these piece because the build up can allow air to pass through. Also, I found my purge selinoid was not closing like is should. The vapor purge selinoid has a passage to the back side of the throttle plates and can allow un metered air in to the engine. Also, check to make sure your air filter box is sealed properly. If this all fails in resolving the problem there is the possiblity of the injector O-rings having a sealing failure.

To cut it short, look for a vaccuum leak before suspecting the sensors. You can do the above steps in any order, but dont start shotgunning with buying parts until it is fixed. I only wish I had done all the check first before shotgunning with parts. I have found several vacuum leaks in mine and it is annoying.

 

thanks. A very through response. I should have noted that there's no 'check engine' light coming on, but I'll do a code read anyhow.

 

I was not getting the check engine light either, but did find a code for the EGR position sensor was out of range. Also found that the EGR vacuum switch was bleeding air back into the vaccuum can. I think the switch was messed up when the EGR vacuum line broke and pieces were sucked back into the switch. The switch controls the bleed back to the egr as well as vacuum, so it was always bleeding air to the egr as well as to the vacuum system. It is hard to actually pinpoint the problem with the idle because so many pieces and parts go into determining how the engine will idle that the computer does not control. I wish you luck in resolving this issue.

 

ok, I brought the rpms down, but haven't solved the problem. I unplugged the power to the seleniod on the driver's side of the throtttle body. I was staying open and letting air into the system. It's a temporary 'fix'.

Here's an interesting thing: Removed the air cleaner and large intake hoses. I sealed off the throttle bodies and and smog pump, and the engine still ran.

Where's the air coming from? Intake manifold gasket leak?